Signal-interpolating system



April 7, 1931.

w. A. KNooP SIGNAL INTERPOLATING SYSTEM Filed Feb. 28, 1929 4 Sheets-Sheet I m.1 w NN w- E mm@ v P :-LIIWIWM Ul W. A. KNOOP April 7, '1931.

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A TTUHNEY April 7, 1931. w. A. KNooP SIGNAL INTERPOLATING SYSTEM 4 Sheets-Sheet 4 Filed Feb. 28, 1929 GERS@ Patented Apr. 7, 1931 U'Ni'isn srafijss `PATENT or-Fics 7 WILLIAM A. KNoor, or i-z-iiiarsrniin,

LABORATORIES, INCORPORATED, or vizoRK Y f NEW YORK, 'ASSIGNOR yTVO BELL TELEPHONE NEV YORK, N. Y., A CORPORATION'OF NEW SIGNAL-'IIN'IRRPOLATING ysYs'rnivI i Apjpimaaon inea February as, 1929. jseriai Naam/152.

This invention relates to synchronous telegraph systems and particularly to interpolating 'receiving-systems for use in high speed telegraph conductors vsuch as loaded submarinecables.

Theobjects ofthe invention are to simpliy and to increase-the effectiveness of interpolat- .ing receiving systems.

Another ob3ect is--to repeat-thesignal`im-r zif? ,pulses from a plurality of low speed lines -into a. single high speed line, and, after transmission thereover, to interp'olate the signal yimpulses which have been lost during transmission and retransmit all impulses corre- 15 spondingfto those at the originating end into a pluralitynof lines.

In high lspeed signaling transmission systems short signal impulses are attenuated fbecauseof the characteristics of the transmission line, and must be'rebuilt'at the receiving end lor the relaying point. Heretofore, systems adaptedto accomplish this purpose have have been commonly termed vibrating relay systems. This expression is Vpractice,heretofore, to interpolateat the rey ceiving ,end of a telegraph circuit" missing signal impulses of unity length which have during transmission. I

Applicants copending application Serial No. 329,4393filed December 31,1928, discloses linterpolating.systemsin each of whichthree or morereceiving relays are employedfthe 15 .relays being so arranged ythat theline voltbeen practically completelyI attenuated ages and interpolating voltages arevsuperimposed on thesame windings of each relay.V

rlhe relays are arranged in rotation to-simultaneouslyrece-ive the incoming signal impulses andthe interpolating voltages, the

Alatter being of suiiicient strength to operate the relays when and only rwhen the incoming signal impulses are of unit length and vof alternatepositiveand negative polarity. The

interpolating .voltages are y generated by a localsource of current andimpressed'on a circuit extending over the contacts of any Y one of the relays through a resistance wherein a volta-ge is regenerated andimpressed "on the windingof the next `succeeding relay.

The systems of the presentinvention dii'ter from those previously kno-wn in that only two receiving relay circuitsof thetype disclosed in the applicants copending application, supra, are employed. These systems comprise arrangements in which'the time derivative of the received signal impulses instead of the signal impulses themselves, `are impressed on the relay windings. The derivatives or voltage impulses, particularly those resulting `from the 'signal :impulses which were transmitted as impulses of two or more Y 1 units length, are of suflicient strengthV to operate thek relays to opposite positions, whereby the relays in conjunction withthe rotary Vdistributor reproduce the signal .impulses of two or more units lengthland produce when impulses Aof unit length'aretransmitted, impulses of alternate, positive and negative polarity, properly timed.

The line .voltages only, are impressed on the relay windings, whereasthe interpolated 'impulses-are producedover the relay contacts as the printer brushes rotate over their .re-

spective segments when the line voltage is of'insufiicient strength vto operate the relays.

In the dra-wings Figs. l and 2 show a schematic circuit of an arrangement in which two receiving relays are employed to repeat the kimpulses from a pluralityV of groups of` transmitters, there being two transmitters in each group. The impulses of each two transmitters are interleaved for transmission over the line, and are repeated through the receiving relays to their respectively associated printers over two separate dis tributor rings.

Fig. 3 shows curves representing the operation of the circuit arrangement shown in Figs. 1 and l2.

Fig. 4 is a modification of the receiving circuit shown in Fig. 2 wherein vacuum tube storing and impulse lengthening arrange ments are used in conjunction with the receiving relays.

Fig. 5 is a modification of Fig. 4l wherein one pair of distributor rings is provided for the operation of the printers and the printer selector magnets are connected directly to the receiving relays.

Fig. 6 is a modification of Fig. 5 wherein 'the impulses from each transmitter are received consecutively, no interleaving of iin- 'pulses being required.

Fig. 7 is another modification of Fig. 4 wherein the incoming' line signals are received in the windings of a high permeability impulse coil'and reproduced therein as short Y sharp voltage pulses, a pulse being produced ,every time the signal current passes through values slightly above and slightly below zero. Fig. 8 shows the curves Vrepresenting the operation of the circuit arrangement shown in Fig. 7.

Fig. 9 is a modification of Fig. 7 wherein the incoming line signals are received in the windings of two high permeability impulse coils connected in series and biased in opposite directions. rlhe signals are reproduced in the coil windings as short sharp voltage pulses every time the signal curieiit passes through values adjacent to that of the biasing current.

Arranging F ig. 2 at the right of Fig. l, a system is shown wherein six transmitters A,

B, C, D, E and F at staton X are respectively y connected in rotation over cable 2O to a corresponding number of printers designated A',

- B, C, D', Fi and F at station Y. The cable is designed for high speed transmission and in order that low sped lines may be connected thereto at the sending end, the transmitters in Fig. 1 may be replaced by a plurality oi' rei lays (not shown) operably connected to low speed lines. T iese relays may be substituted for thev transmitters in a manner described in applicants eopending application,'supia.

transmitters are interleaved on the cable. Y

This is because slow-acting repeating relays or selector magnets are not capable of iesponding to the impulses when received successively from each transmitter in rotation. The interleaving operation consists in connecting the transmitters of each group to the distributor 2l so that the impulses, one from each transmitter of a group, are sent successively until all five impulses of each transmitter of the group are sent. in other words, an impulse from transmitter A is followed by an impulse from transmitter B and this operation is repeated until all five impulses from transmitters A and B are sent. Transmitters C and D and E and F are similarly connected to the sending distributor 2l and these are operated in the same manner as that described above for transmitters A and B.

rilhe impulses from transmitters A and B are received at station Y in an amplifier 22 (which may include shaping networks) and impressed on a small capacity condenser 23. Connected across the output circuit of the amplifier and in series with the condenser 23 is ,a comparatively small resistance 24. The

output circuit is completed by brush 25 in rotating over the ring set 26. Therefore, the signal impulses are impressed on ring set 26 as voltage pulses of short duration, one pulse occurring at each rise and fall of a received signal. The ring set 26is constituted of two rings, one continuous and one segmented. The segmented ring consists of alternate live and dead segments, the alternate live segments being interconnected to form two groups. rFliese groups are respectively conneet-ed to receiving relays 27 and 28. These relaysaie of an unbiasedpol'arized type. In this manner the receiving relays are ai'- ranged to be alternately connected to the cable 2O for that portion of the time when Athe incoming signals are rising and falling through their greatest ampiitudes-` ln high speed operation the signals of unit impulse length are not present in the received signal and any impulse that operates a receiving relay must be one forming a part of a signal of at least two units in length.

' The armatures of relays 27 and 28 are respectively connected to two printer ring sets 29 and 30, each of which comprises a continuous and a segmented4 ring. The segmented rings each consists of ten alternate live and dead segments for each transmitter so that for the six transmitters arranged in three groups, as shown, each segmented ring has thirty alternate live and dead segments. The printer rings are concentrically arranged with the receiving ringset 26, one

fir uw ance 24, both of which have acompar rent producing them* and arey impressed on n different 'lilvef segments off the receiving. set v 'are vrespectively connected to sion, is efectedby 'brush arm being provided with the brushes `for thefthree ring vsets disposed in radial alignment. The live and dead segments of the Aprinter ring sets are of the one length.

The live segments AQ, A2, A3, A1, and A5, the magnets of printer VZi/,the live segments Bl, Bg, B, BQ, and 'B5 are connected to the magnets of .i i 2.2 irinter B and so on for the remaining live segments, each groupv of vlive beingv connected to the magnets of a printer asvshown. In order to havethe proper sequence'of opera- -tion for theprinters, the segments of each of the two ring sets 29'and 30 are so positioned with respect'to the segmentsy of receiving ring `2G that when a receiving brush 25 on ring set 26 is passing through the center of a receiving or live segment the brush of vthe printer ring set .containing the corresponding live segment, is in the centerof a dead segment immediately at the left hand side of such corresponding live segment.Y In other words, should brush 25 be passing the center of segment A3 of ring set 26, brush 31 would be i in the center of the dead segment immediately to the left of segment A3. Therefore, in accordance with this arrangement of the live segments of ring set 26 and the corresponding segments of ring' sets 429 and 30, printers A, BQC, D, E"'and F will be operated in sequence.

The interpolation o fvimpulses station Y i'to replace those lof'unit length which are lost or greatly attenuated during transmismeans o'f brushes 31 and 32 in rotating over their respective printer rring sets 29 and 30. VVhena long impulse,

that is, `one of two `or `more units length, is

,.receivecl, the current ofthe impulse does not vbegin'to build up toa 'sufficient strength to Operate a receiving relay, until they beginning of thesecondunitso that if two long signal impulses ofi opposite polarity are transmitted successively these impulses when they are received fat stationvY, willA be separated by a Zero interval of approximately one unit length. Condenser 23 and resist tively low value,'prevent the signal current itself 'from entering the relays but produce the firstv derivatives, with respect to time, of the long signal impulses, that is, a short, sharp voltage pulse atthe beginningand at the end of cach long impulse which are of sufficient strength to operate the relays. A derivative, as used herein, may be defined kas a voltage or current `pulse proportional to rate of change perl unitof time in the voltage or current received from the ampliiier 22. The

voltage ypulses vthus produced by each long impulse are opposite in polarity to correspond to the vrise'and fall of the signal curprinters A tions there will'be generated, as brushes between certain channels or of polarities on a "the signal v26 so that thearmatures oftherelaysf27 and 2Sfare, 4in response lto the long impulses, always driven' to ropposite positions at the-end of the impulse. Thearmatures are respectively "connectedto the `continuous rings of printer-sets 29 yandBO. -Inasmuc-h as the live segments of the segmented rings of printer sets 29 and 30 are respectively connected to and "B i andthe live segmentsv for printers'A and B are alternately engaged by their respectivebrushes, it is thereforeseen "that when vno long impulses are being repleirsignaling system,ihas been shown byreversing the batteryk leads-of the transmitters shownlin Fig. 1 at points between adjacent leads of each of tlie'two printer Operation of the' circuit arrangement 0 l Referring'to Fig. 3 a clear understanding of theV method *of interpolating impulses of unit length in a message. Whereofthe trans-` `mitted unit impulses'havebeen lost in transmission, may bek had. .Let curve @representV station Y without attenuation; curve b, the same wave as it .is actuallyrecei-ved at sta- Ytion 'Y with .the impulsesnof unit Vlengthv omitted gcurve c, avv-ave showing the derivay tives of the received impulses produced inthe windings of relays 27 and 28 by the combined action of condenser 23 and resistancey 24;

f curve cl a wave indicating the potentials furover the armature of y nished by battery Y a wave indicating the 'porelay 27; curve c,

submarine cablein amultiwave as it would V,be received1 at pairs of transmitters and also by-reversing the battery Vsets between printers. as shown/in -Fig.-2.'

tentials furnished by battery 33 over the armature ofrelay 28 and curve f, a wave show- 'ing the potentials successively applied to? the printers A and B", C and D, and E Vand F', the last wave corresponding to the trans- -mitted'signal waveshown inf curve a, but out ofphase by oneunit intervalto represent the llag ofthe receiving equipment. In 'curve a, the first, second and third .impulses are of unit length and'of alternately opposite, polarities'but arev so greatly attenuated. that no effective current is received at1station-Y,as` shownfin curve b. The-'fourth and fifth transmitted Aimpulses are of 1'negative polarity and form alongim-pulse andtherefore when this impulsefis received and amplified at station `received and amplified at station Y, rise to a sufficient value to form one impulse extending over the ninth and tenth intervals, thereby forming or producing through condenser -3 and resistance 24 two voltage pulses of opposite polarity as shown in curve 0. The eleventh and twelfth impulses are of negative polarity and also form one long impulse of two units length which when received and amplified, rises to an effective value during the twelfth interval to produce two voltage impulses of opposite polarity as shown in curve c. Curve c therefore shows the first derivatives, with respect to time, of the received signal waves as applied in rotation to segments A3, B3, A5, C1, D1, C2, D3, etc. The application of the derivative impulse to segment As operates relay 27 to its negative position. The application of the opposite derivative to segment B3 operates relay 28 to its positive position. The application of the positive derivative to segment A5 operates relay 27 to its positive position. The application of the negative derivative to segment C1 operates relay 28 to its negative position. The application of the negative derivative to segment D1 operates relay 28 to its negative position and the application of the positive derivative to segment C2 operates relay 27 to its positive position. Assume,for the purpose of illustration, that relays 27 and 28 and brushes 31 and 32 are in the positions shown in the drawing. As brushes 31 and 32 rotate and brush 31 engages segment A1 the positive pole of battery 33 is connected through the winding of the first magnet of printer A to the positive pole of battery 34, but the magnet does not operate. As brush 32 reaches segment kB1 the negative pole of battery `33 is connected over the armature and left hand ffl contact of relay 2S through the windings of the first selector magnet of printer B to the positive pole of battery 35 and this magnet of printer B opera-tes. lVhen brush 3l reaches segments A2 a positive potential from |cattery is impressed over the armature and right hand Contact of relay 27, through the windings of the second selector magnet of printer A, and this magnet of printer A also remains unoperated. When brush 32 reaches segment B2 relay 28 is still in its negative position and a negative potential is therefore impressed on the second selector magnetof printer B to operate the second magnet of .printer B. lVhen brush 3l reaches segment A3 a second unit of thefirst long printer A.

signal impulse has been received and amplified shown in curve and has produced a negative voltage as shown in curve c to operate relay 27 to its negative position. A negative potential is therefore applied to the windings of the third selector magnet of printer A which effects its operation. As brush 32 approaches segment B3 the amplied current of the first long signal impulse has decreased to Zero value which permitted the discharge of condenser 23 to produce a voltage impulse of positive polarity to thereby operate relay 23 to its positive position, and therefore the positive pole of battery 33 is connected to the positive pole of battery 35 through the windings of the third selector magnet of printer B', but this magnet does not operate since the batteries are connected in opposition. l/Vhen brush 3l reaches segment Afl, relay 27 is still in the negative position and operating current flows through the windings of the fourth yselector magnet of .Vhen brush 32 reaches segment Bet relay 23 is still in a positive position and no current flows through the windings of the fourth selector magnet of printer B. When brush 3l reaches segment AQ, the current of the second unit of the second long impulse produces a voltage impulse through condenser 23, .as shown in curve c, to operate relay 27 to its positive position, thereby impressing an ineffective positive potential on the fifth selector magnet of printer A. Vhen brush 32 reaches segment B5 the amplified signal current which remained at a steady value during the ninth and tenth impulse intervals, holds condenser 23 in a charged condition so that no impulse is produced to operate the relayv28 and therefore the relay causes an ineffective positive potential to be impressed on the windings of the fifth selector magnet of printer B. This operation is continued for the printers C and D in accordance with the waves shown in curves a, b and c, except that the polarity of the effective potentials for the selector magnets is reversed between each pair of channels as shown in the connection of the printer magnets to batteries 34 and 35. Therefore, in accordance with the signal wave of curve a, only the third and fourth selector magnets of printer A and the first and second selector magnets of printer B are operated to produce the first two desired characters.

By arranging the armatures of relays 27 and 23 to be respectively connected in alternate order to the printers A and B, then to C and D and E and F in turn, it may be readily seen from a study of curves d and e that by selecting the potentials produced by relays 27 and 28 as brushes 3l and 32 rotated over the live segments of their respective ring sets 29 and 30, a wave such as shown by curve f will be produced. It will be noted that this wave includes the impulses of unit length as that/it isout of phase'with curve L by one impulse interval because of the time lag of the receivingapp'aratus'. n

cscmptz'o'a of lthe circuit 'of Fig.

p Arranging rig. i 'at ai@ right of rig. i pigvidfes a system similar to'that shown in 1k and v2 yezfcept'that each o'fthe relays 27 and 28 are 'operated-tliroughtlie action of-a pair of three-electrode vacuum tubes wherein al normal balance of space current valuesis upset in order to control the operation of the relay `associated therewith. ln vFig. 4 the relays l27 and 28 areassuined to be in op'l'io-site positionsso that Twhen thereare rnosign'als be-I ing received yat stationjY the impulses. which are interpolated will'be alternatep'ositiveand negative polarity. Furthermore, when no signals lare being received thenornal balance yof the space current yvalues between the tubes of pai'r remains unchanged, this bal'- ance being upset vonly when signals of tivo or morer units length are received.l Therefore the operationof the arrangement shown in 4`-during 'tl'ie time when the 'impulse'sof unit length are ineffective to operatethe relays j27 and 28, is identical with that d'escirib'edabovefor2. A

When "the long `negative signal, ymade 'up ofthe fourth and fifth impulses 'shown in curye a of Fig.'3`, isreceived, the current `of the second unit impulse during the fifth interval increases to an' amplitude vsufficient to produce anegative voltage acrosszc'ondenser 23. This vpotential is applied through ring vset i26 by means of brush 2 5 passing over tov condenser 36 and the grid lsegment A yof vacuum tube 37. Battery 38 is also applied through ringfset 26 to thel grid ofvacuumtube 37 yto give it I,a normal negative bias.

The negative potential receivedfi'oniv ycon'-k denser 23 malesthe' grid'mo're negative with respect rto its associated filament and causes a negative charge to bestored on condenser 36.l As'brush 25. passes olf seginent A3, the voltage 2storedon Condenser 36prolongs the negative potential impressed on the grid by the signal itself; i Consequently, the normal space current in'vacuum'tube 37 is decreased. The second'vacuum tube 39 of the first pair has'it's grid .normally biased negatively with respect toits 'filament'bya battery 40 and the fvariatio'n'in the space'current of tube 37 is effectivefin aresistance 41 to cause a voltdrolit'o` be produced" across thei'esistance infsuch direction `that a negatiye potential is iii'ipress'ed on condenser 42 to'malre the of tube 439 less negative, thereby 'causingan increase in the normal space" vcurre'nt"of tube 39. l Resistance 43 A:serves to balancethe normal s ace'current ofntub'e 39 with'thatof tube-3 The windings ofY relay :27 jare :conne'cted in 'series to the .plate` circuitsv of tubes lthe grid of and-39 in such manner thatthe lequal normalfsp'ace currents of tubes 37 and 39 neufv tralize each others magneticeifect on the relay. y Connected in the Vplate circuit of tube 37 and in shunt'to relay 27 isl resistance 44 and ,in the plate circuit o-ftubeand also in shunt to relay 27 is resistance '45. y

Any changes inthe space current of tubes 37 and y39, causes a vdifference of potential to occur across the windings of relay 27 and the relay operates l'to either. of` its contacts dcpendingnpon thedirection `of the voltage drop caused Athe increase and decrease of thegspace currents of tubes 37 and 39. In the present case, the decrease in space cur-` rent `of tube 37 together with the increase in spacecurrent vof tube 39cause relay 27 toopeiate vitsarma-ture toits left hand contact.y

When brushv reaches segment B3 the i signaling current as shown in curve ZJ' of Fig. 3 decreasesto Zero which permits the discharge of condenser 23 and an impulse of positive Vpotential is'now applied to con-v denser 46 andgrgrid of vacuum tube 47 of la secondpair. Battery 38 is also applied to i vtube 4c7 to give it a normal negative bias ybut the Vpositive potential applied by the discharge of condenser 23 makes the gridy of tube 47 less negative with respectto its filamentand 'the space current thereof is increased. The function ofconden'sei1 46" serveswhenbrush 425passes off segment Bg',

the grid of vacuum tube 47. i rlhe second vacum tube 48"of the second pair has its grid to prolong-the positive Lpotential impressed on l its filamentby battery 40`a'n`d yas lthe space current of tube 47 flows through a 'resistance 49 a voltage drop is produced across kthe rey sistance in such a direction that apositive potentialis'impressed on condenser 50 to make the grid `of tube 448 more negative, Athereby causing` a decrease in the'spacey currentin tube '48. The vwindings of relay 28 y'are connected in vseries to the fplate circuits of tubes 47 and 48 and in ysuch manner that the normal space, currents neutralize each other in the windings of relay 28. Resi'stanc'es 5l `and 52 areconn'ected in the plate ,circuits oftubes f 47 and 48, respectively-and any change inthe l voltage drop across these resistances upsets thebalanced condition of relay 28-and` causes it to operate its 'armature to either .of its yas'- soci'ated cont-actsinaccordance with the predominating changefin voltage. `VFor instance, in thepresent case where t'heispace current of ltube 47 "is increased and the spacel current -of-tu'be 48fis decreased because ofthe positive potential-received over segment lB3 andl'br-u'sh '25, the armature of relay 28 inoves toits right hand-contact, A f n p The; interpolated' jnpulses gare produced in the saine-manner as described-'above for Fig;

2, where it was stated that the relays were operated to opposite positions at the beginning and end of each long signal impulse and the relays 27 and 2S were alternately connected to their respective printers A and B, C and D, and E and F in rotation.

In this arrangement inA which pairs oi vacuum tubes are provided for effecting the balance of opposite potentials acrossV the windings of thereceiving relays, it is possible to have a perfect balance across each relay, while the sensitivity of adjacent relays and their associated tubes will be dilierent, and thereforein order'to equalize the sensitivity of the relays 27and 28, the plate battery 53 is adjustably connected to a resistance 54.

Description Aof circuit ofFz'g. 5

The arrangement shown in Fig. 5 is substantially the'same as that shown in Fig. 4L except that a single printer ring set is employed and the selector magnets of the printers are connected between the relay contacts and the live segments of ring set 55, the armatures of the relay being fiXedly connected to positive battery 56. The vacuum tube circuits comprising elements 36, 37, 39 to 54, inclusive, as shown in Fig. 4, 'are represented diagrammatically by block 57. Assuming that the spacing and marking impulses from transmitters A and B at station X `are positive and negative, respectively, relay 27 will operate to its left hand Contact for each negativeimpulse received from station X and to its right hand contact for each positive impulse received. Therefore, in response to the marking or negative impulses, positive potential from battery 56 is furnished over the armature of relay 27 to operate the magnets of printer Af in accordance with the marking impulses. Relay 28 will likewise operate to its left handcontact in response tothe Vreceived.marki.ng or negative impulses to connect positive battery over its varmature to the magnets of printer B in accordance with the received marking impulses. No magnets of printers'A and B are operated in response to received spacing or positive impulses. Assuming likewise that the spacing and marking impulses in transmitters C and D are reversed in polarity, relays 27 and 28 will operate to their' right hand contacts in response to received marking or positive signal impulses and to their ht hand contacts in response toV received spacing positive signal impulses, the magnets not responding when the lrelays operate to their left-hand contacts. Relays 27 and 28l being in opposite positions during the timesfwhen no signals are beingreceived, potentials of opposite polarities will be alternately applied to the magnets of printers A and B', C and D4 etc-'as brush 58 rotates over ring set'55. f

Description of the cz'ro'm't of Fig. 6

, The system shown in Fig. 6 is similar to that of Fig. 5 and is shown in part only, it being understood that what is shown may be employed in place of the equipment shown below the line za in Fig. 5. Fig. 6 therefore represents a. system which is the same that represented by the schematic arrangement shown in Fig. 5 taken in conjunction with Fig. l, except as noted below. The transmitters at station X are connected to cable 20 so that the impulses of each transmitter are consecutively transmitted instead of being interleaved with those of another transmitter as shown in Fig. 1. Accordingly, assuming that all transmitted impulses are received at station Y, the impulses from transmitter A are received on the first live live segments of receiving ring set 26; the impulses from transmitter B, on the second live live segments; andv so on for the remaining transmitters. The live segments of ring set 26 are alternately arranged in two groups which are respectively connected to relays 27 and 28 like those shown in Fig. 5, but in this case each of the relays receive alternate impulses from each transmitter instead of all the impulses from a transmitter. The segments of that the selector magnets of each printer in turn are capable ol' being consecutively connected by brush 60 to the armatures of relays 27V and 2 I The armatures of relays 27 and 28 are connected to the positive pole of battery 6l and the selector magnets of the printers A', B, C, and D are operated in response to marking impulses transmit-ted from station X. The marking or operating impulses from transmitters A and C operate the relays to their left hand contacts and the marking or operating impulses from transmitters B and D operate the relays to their right hand contacts. The interpolated impulses are produced in the selector magnets in the same manner as described above except that only one printer ring set like in Fig. 5 is employed.

The arrangement shown in Fig. 7 is another vmodification of F ig. Il wherein an impulse coil 62 of the type disclosed in a copending application of E. T. Burton (Case 7), Serial No. 280,709, filed May 26, 1928, Fig. 7 of the drawings thereof, is employed in between cable 20 and the input circuit of vacuum tube amplifier 63. The nature of the impulse coil may be briefly described as a winding having a core of small cross-section ot' aA high permeability material such as permalloy. The magnetic circuit of the transformer becomes saturated at a low amplitude of signal current in the primary winding and the inductance is consequently almost zero printer ring set59 are arranged so 9 CII except when the core is demagnetized, lthat is at low signal amplitude. Then the permeability is high, thev indu'ctanceot the priinarywinding rises fto a high value andithere is-produced inthe secondary winding of the transformera voltage impulse, the yintensity and duration off which are regulated `by the electrical constants oiithe transformer and.

- the correspondingimpulses TheA voltage impulses produced in the secondary winding areimpressed on the vacuum tube. 63v

wherein they are aiiiplified,and passed'without any appreciable Leiiect through blocking condenser 7 5, which 'serves' merely to block the passage oft the direct current component of the ampli'iied impulses. :The remaining part of the 4arrangement shown inFig; 7 functions the same as l.V l

Description of theci'rcmf 0f F 9 Fig. 9 is a'modiication of that part ofFig. 'i' to the'left ofline -b wherein two transformers 64 and fcomprising impulse coils, l are shown connected in seriesbetween cable 2O and vacuum tube amplifier 63.v Thetrans' former impulse coils areoperated in a man# ner described in detail in the application of E. T. Burton, supra, and shown `in Fig-870i? the drawing thereof. Coils 66 and67 represent the primary windings and `coils 68 vand..

69 Y areithe secondary Vwin dings.' The transformers arevbiased by a direct lcurrent {lowing in opposite directions through-biasing windings 70 `and 71. The 'opposite biasing windings prevent the signalingcurrent flowing in vthe primary windings trom producing an effective inductance until'th'e magnetomotive force-ot theprimary current becomes nearly equal, and opposite, to'that vofthe current in either of the biasing windings. When these lmagneto-motive lforces become equal'the inductance risesft-o a high value aliiiost instantly ftoproduce a volt-ageimpulse inf one 'of the secondary windings. This voltageimpulse is short andsharp because the magnetic circuit' becoinesjquickly `saturated or overloaded. Therefore, .thev signaling current is eliective to produce a kvoltage impulse in either of the secondary windings only in those intervals in which the current is passing through the narrow range of values in the neighborhood of the biasing current ainplitiide, jwher'ein the inductanc-e .jrises to a -high'yalue. `"The inductance 'rises toqsuch value twice in each positi'vevand "each nega. tive sweep-ofthe signaling lcurrent wave ln order to .insure these voltage Y impulses 'being the biasing windings. In order to provide an improved 'shaping .for thefsecondaryivolt.-

age impulses a resistance-'capacitynetwork l "73 may be `provided intermediate theA trans-j torinersand vacuum tube amplifier 63. 1

Fig. 10 shows in curves a, b and c the :priJ mary current wave, the secondary voltage wave, Aand the secondary voltagel Wave fatter shaping and ampliication, respectively. [The dotted parallel lines m andy in-curve 'la-rep# resent tlieranges of amplitudes inwhich high inductance values are attained whereatvthe voltage impulses, shown in curve b, occur. Curve cshows the shape ofthe signal gimpulses desired to impress upon the storing condensersin the vacuum tube circuits ydiagrainmatically represented by block 57.

-l'lows the signal to pass but blocks thedirect current componentV of the voltage 'imf pulses in `plate circuit. lfihat is claimed is:

l. An impulse transmission system in Y ber of units racts oneach ofthe relays, one fat the secondunit kand one at theend ,oi the im'- pulse to-reverse their positions;a`nd a .plu-

Condenser' 75 isa blocking condenser. which ioo ral unit impulse otanjeven numberotunits i aotsron one only rof the relays, once at the second unit and again'atthe'end ofthe v1mrpulse to reverse andrestore its position..

' 2. ln a telegraph system comprising a .pluralityvof receiving relays, the method which comprises taking the derivativesproducedat the beginning andend only yoi" each received impulse and .applying said `derivatives in ro tation to said plurality of receiving relays.

3.4i synchronousl interpolating system` characterized in this that it comprises a line having a liigliattenuation characteristictor transmitting signals, a pair of relays, a single pair of ydistributor rings whereby said :relays are alternately 'connected tosaid line',- said i relays beingcapable through the single -pair 'of distributor rings oi beingoip-)erated bythe iirst and last derivativesonly, with.respv'ecttov time, of each ot the received impulses and of assuming relatively opposite-.positions when no signals are lbeing received, and other mea-ns for yfurther repeating'the signalsfre-` ceivedirom saidline and-inserting inethe'ffre ceived signals impulses of alternately oppof site' ypolarity to replace'lthe impulses; that are lost .during transmission over said .line

Ll-.f4 A'telegra'ph system comprising-.a transf mission line 'having fa "high attenuation 'than acteristic, a single pair of receiving distributor rings, a pair ot relays arranged to be alternately connected to said line through said pair of distributor rings, and means connected between saidline and said pair of distributor rings for producing in response to each received impulse which was impressed on said line as an impulse of two or more units length, a pair of short, sharp voltage impulses, one at the beginning and the other at Vthe end of each received signal impulse, to operate said relays, the voltage impulse produced at the end ot veach received signal impulse being effective to set the relays in relatively opposite positions.

5. A telegraph system comprising a transmission line, a single pair of receiving distributor rings, two relays arranged to be alternately connected to said line through said pair of distributor rings, Vand a capacity-resistance networl: connected between said line and said pair of distributor rings for producing an impulse at the beginning and end ot each received impulse to operate said relays, the impulse produced at the end oi" each received signal impulse being effective to set said relays in relatively opposite positions.

6. A telegraph system comprising a transmission line, a single pair of distributor rings, two relays arranged to be alternately connected to said line through said distributor rings, means connected between said line and said distributor rings whereby the derivatives only of the received signal impulses are utilized to operate said relays, said relays being operated to relatively opposite positions in response to the derivative produced at the end of each received signal impulse, and means for normally impressing across the windings of each of said relays equal potentials of opposite polarity whereby the relays are normally maintained unenergized, said means heilig effective in response to a signal derivative to vary the potential across the winding of either of said relays whereby the relay is operated to its opposite position.

y 7. A telegraph system in accordance with claim 6 characterized in that it Vcomprises means for equalizing the sensitivity of said relays. 'A A I 8. A telegraph system comprising a transmission line, a. single pair of distributor rings, a pair of relays arranged to be alternately connected to said line through said distributor rings, capacity-resistance network connected between said line and said distributor rings whereby the derivatives only of the receivedl signal impulses are utilized to operate said relays, said relays being operated to relatively opposite positions in response vto the derivative produced at the end of each received signal impulse, a pair ot vacuum tubes arranged in push-pull cascade arrangement fork normally impressing across the Wlnding of'each of said relays equal posaid pair ot distributor rings tentials of opposite polarity whereby the relays are normally maintained unenergized, said vacuum tube arrangement being citeetive in response to a signal derivative to vary the potential across the winding of either of said relays whereby the relay is operated to its opposite position, and means connected in the circuits .of said vacuum tubes for equalizing the, sensitivity of said relays and said pairs ot vacuum tubes.

9. A telegraph system comprising a transmission line, a single pair of receiving distributor rings, a pair of repeating devices arranged to bealternately connected to said line through said pair ot distributor rings, and means connected between said line and u for producing the first and last derivatives only, with re spect to time, ot the receivedsignal impulses to operate said repeating devices, the derivative produced Vat the end of each received signal impulse being edective to set the repeating devices in opposite positions.

l0. In a multiplex telegraph system, a sending station and a receiving station, a transmission circuit interconnecting said stations, a plurality of transmitters at said send- 'ing station, means for applying signal impulses trom said plurality of transmitters to said circuit in rotation, the impulses of one transmitter interleaved with those of another transmitter, al pair of receiving relays at said receiving stat-ion, and means at said receiving station for producing a. signal derivative at the beginning and end of each received signal impulse and tor applying the derivatives to said receiving relays, whereby the relays are operated to opposite positions in response to the derivative produced at the end of each received signal impulse, a plurality of printers arranged in pairs at said receiving station, a pair of printer distributor rings arranged to alternately distribute the impulses produced by said relays over each pair oit printers in rotation.

11. A telegraph system comprising a transmission line, a single vpair of receiving distributor rings, a pair of relays arranged to be alternately connected to said line through said pair ot distributor rings, and means comprisng differentiating devices connected between said line and said pair oi distributor rings for producing a signal derivative at the beginning and at the end ot each receivedsign'al to operate said relays to opposite positions, said impulse coils being ef- `teetive to produce the derivatives during any desired range ot rising and falling amplitudes of the signal impulses of positive and negative polarities.l

12. A telegraph system in accordance with claim 1l in which the differentiating devices include a network of impedance. l

13. A telegraph system in accordance with claim 11 in which the differentiating devices include capacity-resistance networks.

14. A telegraph system in which impulses of unit length sent from a transmitter but not received in effective amplitude, are re-` generated, and impulses of plural unit length are received, characterized in this, that the impulses arriving are distributed among an even number of relays each having a single operating winding, alternate relays remaining normally quiescent in opposite positions for the regeneration of unit impulses, and are operated at times by derivatives only of the current impulses through their respec tive single operating windings.

In witness whereof, I hereunto subscribe my name this 26th day of February, 1929.

' WILLIAM A, KNOOP.y 

